I found this when I was searching for my choice of AI and this is my response to this question when I see it or hear it:
"Arimidex is not a good aromatase inhibitor for men. Stick with aromasin. Arimidex is a weak inhibitor of E2(it's strength is inhibiting E1 in women. Not well suited for men). It's also a competitive inhibitor (not a suicide inhibitor) so you'll get a rebound when you come off or need a higher dose. Aromasin is a much better solution. It binds to the aromatase and kills it. So there is no rebound and stops more E2 production.
Arimidex is a competitive inhibitor so it competes for the binding site of the enzyme with testosterone and blocks it from getting converted to estrogen. It's not very good at it, but that's what it does. So the enzyme is still present in large numbers because your body overcompensates. When you stop the Arimidex the blockade is gone and the E2 levels soar. That is why suicide inhibitors like aromasin are preferred.
When it comes to this comparison its more about type of estrogen suppression as opposed to "strength". Arimidex is a VERY potent sulfatase inhibitor, which inhibits estrone. It is a moderately strong aromatase inhibitor (weak as compared to aromasin, AIFM or letrozole). This is fine for women with breast cancer who produce percentage wise very high levels of estrone (the weak estrogen), which can be converted to estradiol (the strong estrogen) via aromatase.
For men this is generally not very good, especially for men on TRT since sulfatase inhibitors have very little effect on exogenous testosterone. Actually its generally not a good thing since it nearly completely eliminates estrone, while still allowing estradiol. If you have a choice as a man, you want estrone (weak estrogen) with near total elimination of estradiol (strong). AIFM and aromasin do inhibit sulfatase, though to a lesser extent than the competitive inhibitors (dex and letro). They are both potent aromatase inhibitors and highly suppress estradiol. Since exogenous test converts to estradiol via aromatase, AIFM and aromasin are much better suited.
Lowest doses of letrozole completely suppresses glandular production of estrone(E1). while it generally takes higher end doses of exemestane (aromasin) to come close to doing this. Exemestane dose dependantly decreases estradiol and to a lesser extent estrone. Basically aromasin at low doses is mostly peripheral, which means blocking conversion of estrone, testosterone and other aromatic precursors to estradiol. Whereas because they are competitive inhibitors that have high permeability through tissue types, arimidex and letrozole have high affinity and saturation of tissues like testes and adrenals, where estrone is produced. They highly block synthesis of aromatase in those tissues at even lowest doses."
I am going to go with aromasin. But I will have one of the others on hand to experiment should aromasin be failing me, was bunk aromasin, or for experimentation. I have not had my first cycle yet so this is not my personal experience. Just something I thought sounded well thought out.
